In certain fuel systems, such as for vehicles, a pump is provided to move fuel through the system such as from the tank to the engine. A filter element is typically provided upstream (on the vacuum side) of the pump to protect the working components of the pump, as well to protect other downstream components. When the pump is initially primed, air in the filter housing is purged to the extent of the fuel flow through the filter element. When the element is fresh, and only a small portion of the media is being used, this can amount to only a small portion of the air in the housing being purged. As the filter element becomes filled with contaminants over time, the resistance increases and the housing will be purged of a little more air until the fluid will pass through the media easily again. By the end of the element's life, the housing will be full of fuel, and the air will be substantially purged from the housing.
The constant purging of air in the housing does not significantly effect the particulate and contaminant separating functions of the filter, but it can impact the water-removing properties of the media, as the flow is forced through a relatively small portion of the media at a high rate, rather than being spread over a wide surface area. It is preferable to have a wide surface area used to take full advantage of the water-removing capabilities of the filter media.
One solution, particularly for vertically-oriented filter elements, is to provide a bleed orifice in the upper end cap of the filter element. The orifice allows the air to bleed slowly out of the element as the element is being filled with fluid. By sizing the orifice appropriately, and locating the orifice in the upper end cap, the orifice will essentially only allow air to vent out, and will substantially prevent fluid leakage. Any bypass of unfiltered fuel is fairly insignificant and can be caught by secondary filters downstream. By so doing, the fuel fills substantially the entire housing, and passes slowly across a large surface area of the media for efficient water removal.
While the above solution has received some acceptance with vertically-oriented filter elements, it does not address the issue with horizontally oriented (side-loaded) filter elements. Some applications, such as in fuel delivery systems for vehicle engines, require elements to be “side-loaded” due to the location of engine components. For such applications, the elements are typically coupled to the housing cover for ease of insertion and removal. But in so doing, the elements rotate when the cover is screwed down onto the housing. When the filter rotates, it can be difficult to anticipate and control the final location of the vent orifice, and hence to position the vent orifice such that it allows a maximum amount of air to vent from the element. As should be appreciated, positioning the vent orifice, for example, at the bottom or near the bottom of the element will not allow air to be purged from the element.
Thus, it is believed there is a demand for a filter element and assembly for fluid applications which require a purging of air, and particularly for such applications where the filter element is horizontally oriented (side-loaded), where the filter element is rotationally positioned such that the vent orifice is properly located for bleeding air from the filter element as the element fills with fluid.